1. Field of the Invention
The present invention relates to contact charging devices for charging the outer peripheral surface of a photosensitive member in contact therewith for use in image forming apparatus such as copying machines and printers.
2. Description of the Background Art
Electrophotographic copying machines, printers and like image forming apparatus produce copies or prints by charging a photosensitive member with a charging device, exposing the charged region of the member to an optical image to form an electrostatic latent image, developing the latent image to a visible image, transferring the image to a sheet and fixing the image thereto.
Various types of charging devices are known which are classified generally into corona charging devices utilizing corona discharge, and contact-type charging devices having a charging brush, charging roller, blade or drivingly rotatable endless charging belt adapted to contact the surface of the photosensitive member.
The charging device utilizing corona discharge has the advantage of giving charges with good stability but has the problem of producing a large amount of ozone, which deteriorates the photosensitive member and adversely affects the human body, so that attention has been directed to the contact charging device which is much smaller than the corona charging device in the amount of ozone to be produced.
However, the use of the contact charging device involves the problem that toner particles remaining on the photosensitive member or particles of the photosensitive material adhere to the charging member, permitting the particle-adhered portion to cause uneven charging to produce irregularities in images.
Accordingly, the main object of the present invention is to provide a highly reliable charging device which is capable of affording a uniform charged state with good stability over a long period of time unlike the conventional contact charging device.